spi: sc18is602: fix Wvoid-pointer-to-enum-cast warning

spi: sc18is602: fix Wvoid-pointer-to-enum-cast warning

'id' is an enum, thus cast of pointer on 64-bit compile test with W=1
causes:

  spi-sc18is602.c:269:12: error: cast to smaller integer type 'enum chips' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230810091247.70149-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>